ktlint

ktlint documentation

Version in MegaLinter: 1.4.1
Visit Official Web Site
See Index of problems detected by ktlint

Configuration in MegaLinter

Enable ktlint by adding KOTLIN_KTLINT in ENABLE_LINTERS variable
Disable ktlint by adding KOTLIN_KTLINT in DISABLE_LINTERS variable

Enable autofixes by adding KOTLIN_KTLINT in APPLY_FIXES variable

Variable	Description	Default value
KOTLIN_KTLINT_ARGUMENTS	User custom arguments to add in linter CLI call Ex: `-s --foo "bar"`
KOTLIN_KTLINT_COMMAND_REMOVE_ARGUMENTS	User custom arguments to remove from command line before calling the linter Ex: `-s --foo "bar"`
KOTLIN_KTLINT_FILTER_REGEX_INCLUDE	Custom regex including filter Ex: `(src\\|lib)`	Include every file
KOTLIN_KTLINT_FILTER_REGEX_EXCLUDE	Custom regex excluding filter Ex: `(test\\|examples)`	Exclude no file
KOTLIN_KTLINT_CLI_LINT_MODE	Override default CLI lint mode - `file`: Calls the linter for each file - `list_of_files`: Call the linter with the list of files as argument - `project`: Call the linter from the root of the project	`list_of_files`
KOTLIN_KTLINT_FILE_EXTENSIONS	Allowed file extensions. `"*"` matches any extension, `""` matches empty extension. Empty list excludes all files Ex: `[".py", ""]`	`[".kt", ".kts"]`
KOTLIN_KTLINT_FILE_NAMES_REGEX	File name regex filters. Regular expression list for filtering files by their base names using regex full match. Empty list includes all files Ex: `["Dockerfile(-.+)?", "Jenkinsfile"]`	Include every file
KOTLIN_KTLINT_PRE_COMMANDS	List of bash commands to run before the linter	None
KOTLIN_KTLINT_POST_COMMANDS	List of bash commands to run after the linter	None
KOTLIN_KTLINT_UNSECURED_ENV_VARIABLES	List of env variables explicitly not filtered before calling KOTLIN_KTLINT and its pre/post commands	None
KOTLIN_KTLINT_DISABLE_ERRORS	Run linter but consider errors as warnings	`false`
KOTLIN_KTLINT_DISABLE_ERRORS_IF_LESS_THAN	Maximum number of errors allowed	`0`
KOTLIN_KTLINT_CLI_EXECUTABLE	Override CLI executable	`['ktlint']`

IDE Integration

Use ktlint in your favorite IDE to catch errors before MegaLinter !

	IDE	Extension Name	Install
	Emacs	flycheck-kotlin	Visit Web Site
	vim	ale	Visit Web Site

MegaLinter Flavors

This linter is available in the following flavors

Flavor	Description	Embedded linters
all	Default MegaLinter Flavor	124
c_cpp	Optimized for pure C/C++ projects	54
cupcake	MegaLinter for the most commonly used languages	83
documentation	MegaLinter for documentation projects	49
dotnet	Optimized for C, C++, C# or VB based projects	62
dotnetweb	Optimized for C, C++, C# or VB based projects with JS/TS	71
go	Optimized for GO based projects	51
java	Optimized for JAVA based projects	52
javascript	Optimized for JAVASCRIPT or TYPESCRIPT based projects	59
php	Optimized for PHP based projects	54
python	Optimized for PYTHON based projects	62
ruby	Optimized for RUBY based projects	50
rust	Optimized for RUST based projects	50
salesforce	Optimized for Salesforce based projects	54
swift	Optimized for SWIFT based projects	50
terraform	Optimized for TERRAFORM based projects	54

Behind the scenes

How are identified applicable files

File extensions: .kt, .kts

How the linting is performed

ktlint is called once with the list of files as arguments (list_of_files CLI lint mode)

Example calls

ktlint myfile.kt

ktlint --format myfile.kt

Help content

Usage: ktlint [<options>] [<arguments>]... <command> [<args>]...

  An anti-bikeshedding Kotlin linter with built-in formatter.
  (https://pinterest.github.io/ktlint/latest/).

  Usage on Windows: java -jar ktlint.jar [<options>] [<arguments>]... <command>
  [<args>]...

  # EXAMPLES

  ## Use default patterns

  Check the style of all Kotlin files (ending with '.kt' or '.kts') inside the
  current dir (recursively). Hidden folders will be skipped.

  `ktlint`

  ## Specify patterns

  Check only certain locations starting from the current directory. Prepend !
  to negate the pattern, KtLint uses .gitignore pattern style syntax. Globs are
  applied starting from the last one.

  Check all '.kt' files in 'src/' directory, but ignore files ending with
  'Test.kt':

  `ktlint "src/**/*.kt" "!src/**/*Test.kt"`

  Check all '.kt' files in 'src/' directory, but ignore 'generated' directory
  and its subdirectories:

  `ktlint "src/**/*.kt" "!src/**/generated/**"`

  ## Auto-correct style violations

  Check all '.kt' files in 'src/' directory, and when possible automatically
  correct the lint violations:

  `ktlint -F "src/**/*.kt"`

  ## Using custom reporter jar and overriding report location

  `ktlint
  --reporter=csv,artifact=/path/to/reporter/csv.jar,output=my-custom-report.csv`

  # Options and commands

Options:
  -v, --version            Show the version and exit
  --code-style=(android_studio|intellij_idea|ktlint_official)
                           (deprecated)
  --color                  Make output colorful
  --color-name=<text>      Customize the output color
  -F, --format             Fix deviations from the code style when possible
  --limit=<int>            Maximum number of errors to show (default: show all)
  --relative               Print files relative to the working directory (e.g.
                           dir/file.kt instead of
                           /home/user/project/dir/file.kt)
  --reporter=<text>        A reporter to use (built-in: plain (default),
                           plain?group_by_file, plain-summary, json, sarif,
                           checkstyle, html). To usea third-party reporter
                           specify a path to a JAR file on the filesystem via
                           ',artifact=' option. To override reporter output,
                           use ',output=' option.
  -R, --ruleset=<text>     A path to a JAR file containing additional
                           ruleset(s)
  --stdin                  Read file from stdin
  --stdin-path=<text>      Virtual file location for stdin. When combined with
                           option '--format' the actual file will not be
                           overwritten
  --patterns-from-stdin[=<text>]
                           Read additional patterns to check/format from stdin.
                           Patterns are delimited by the given argument.
                           (default is newline). If the argument is an empty
                           string, the NUL byte is used.
  --editorconfig=<text>    Path to the default '.editorconfig'. A property
                           value from this file is used only when no
                           '.editorconfig' file on the path to the source file
                           specifies that property. Note: up until ktlint 0.46
                           the property value in this file used to override
                           values found in '.editorconfig' files on the path to
                           the source file.
  --baseline=<text>        Defines a baseline file to check against
  -l, --log-level=<value>  Defines the minimum log level (trace, debug, info,
                           warn, error) or none to suppress all logging
  -h, --help               Show this message and exit

Commands:
  generateEditorConfig     Generate kotlin style section for '.editorconfig'
                           file. Output should be copied manually to the
                           '.editorconfig' file.
  installGitPreCommitHook  Install git hook to automatically check files for
                           style violations on commit
  installGitPrePushHook    Install git hook to automatically check files for
                           style violations before push

Installation on mega-linter Docker image

Dockerfile commands :

# Parent descriptor install
ENV JAVA_HOME=/usr/lib/jvm/java-21-openjdk
ENV PATH="$JAVA_HOME/bin:${PATH}"
# Linter install
RUN curl --retry 5 --retry-delay 5 -sSLO https://github.com/pinterest/ktlint/releases/latest/download/ktlint && \
    chmod a+x ktlint && \
    mv "ktlint" /usr/bin/